1. Field of the Invention
This invention relates to machine elements and mechanisms generally, but more particularly to miniaturized motors.
2. Description of the Related Art
Existing designs for canned drink vending machine motors that operate at or above 100 inch-pounds are characterized by heavy duty shaded pole motors, zinc gear boxes, all metal gears with sleeve or needle bearings, and oversized installation envelopes.
In addition, the cost and weight for such designs are among the highest for subfractional horsepower gear motors. For example, present designs for vending machines include add-on brackets for custom mounting. Moreover, it is generally known that shaded pole motors are among the most inefficient types of motors in general use. Exemplary prior art devices are discussed below.
U.S. Pat. No. 5,446,326 issued to Scheider on Aug. 29, 1995, for a vending machine gear motor including a plastic gear box. As shown in FIG. 1 of his U.S. Patent, the gear motor of Scheider comprises a gear box 11 having a generally hollow plastic gear box housing 12, a gear train 14 mounted therein, and an electronically insulating cover 13.
U.S. Pat. No. 5,256,921 issued to Pruis et al. on Oct. 26, 1993, for a gear motor with a rotary switch. The gear motor has an output shaft for driving a dispensing mechanism of a vending machine. As shown in FIGS. 2 and 3 of their U.S. Patent, the gear motor of Pruis et al. includes an electric motor 12 mounted on a printed circuit board 13 and also includes an output shaft 14 which drives a conventional gear reduction unit 16.
U.S. Pat. No. 5,404,060 issued to Nakahashi et al. on Apr. 4, 1995, for a miniature motor with a worm reduction gear. The miniature motor includes a motor section 1 which transmits torque generated from a motor shaft 3 to a worm 4, then to a helical gear 5 in a reduction gear section 2, and eventually to an output shaft 6.
U.S. Pat. No. 5,172,605 issued to Schwartz on Dec. 22, 1992, and is assigned to the same assignee as the present invention. Schwartz discloses an electric motor gearbox for a vending machine. The gearbox has four main parts: a housing, a minimotor, a printed circuit board, and an assembly of plastic gears.
Various other gearing mechanisms relating to relatively small motors of general interest are disclosed in U.S. Pat. No. 5,747,903 issued to Klingler on May 5, 1998 and in U.S. Pat. No. 5,734,210 issued to Keutz on Mar. 31, 1998.
Despite these recent developments, it remains a problem in the prior art to develop a miniaturized motor with high torque for a gearcase which makes efficient use of space in a vending machine.
The present invention features unique improvements in the use of engineering plastics. The layout of components is compact, taking advantage of a direct current (DC) motor position which, in this particular case, is adjacent to a first-stage worm.
This arrangement keeps a miniaturized motor compact inside a gearbox which makes efficient use of space in a vending machine and in any other unit requiring an application of high torque in a small space.
A gear train within a gear box has standard available gears. However, the transfer stage from the worm down to a plurality of cluster gears within the gear box is flexibly arranged for a variety of gear ratios. This flexibility is introduced by adjusting the gear ratio between the first-stage worm with either single, double or quadruple threads and an adjacent pinion gear.
A metallic output shaft is supported directly within the gear box without introducing additional bearings. The lifetime of the gear box for directly supporting the output shaft is very predictable. Thus, this novel arrangement reduces costs over the lifetime of the gear box quite noticeably.
A number of features support quiet operation in addition to the first-stage worm. The gear box has close envelope contours to retain grease in the gear train. This close envelope also aids quiet operation. A plurality of acoustical chambers surround the gear train and insulate against noise transfer.
Unique to the present invention is the pinion gear that is supported by either a boss or a steel pin. Consequently, the invention provides a more stable gear mesh operation. Also, a cover supports the boss for the pinion gear at one end.
The rating of the gear motor can have a direct current (DC) voltage of either 12, 24, 36 or 48 volts. Furthermore, a printed circuit (PC) board is mounted on the gear box. A plastic cover provides a mounting post to support the PC board.
Materials for both the gear box and the cover are acrylonitrile butadinene styrene (ABS) copolymers or other engineering plastics with or without reinforcement in the matrix. Alternatively, metals may be used. However, they are not preferred because of their weight. Gears are made of delrin, nylon or other engineering plastics. Upper stage gears are formed from powdered metal or fine metallic blanks. Thus, the output shaft and other elements for transmitting torque are fabricated out of either powdered metal or metallic blanks.
Grease is selected from the high performance synthetic greases with a tolerance for both high and low temperatures. The poly-alpha-olefins have been found to be most satisfactory in this regard.
A key advantage of the present invention is that no anti-back-drive brake is necessary because of the use of the first-stage worm which typically cannot be back driven.
Thus, it is a primary object of the present invention to provide a vending machine with miniaturized motors that are compact, have noise control features, have higher efficiencies when compared to prior art devices, and are inexpensive to construct.
A secondary object of the present invention is to provide a miniaturized motor for custom mounting to a vending machine by direct foot mounts.